Timepieces of the wristwatch type allowing the user to read the time in the dark are already known. Amongst all these wristwatches, many comprise a dial, typically made of brass, in which are arranged recesses that form the time indices, for example representing the hours. These recesses are then filled by means of a syringe for delivering a phosphorescent material capable of returning at night the luminous energy that the phosphorescent material stored during the day. A phosphorescent material commonly used in high-end watchmaking is marketed by the Japanese company Nemoto & Co. under the brand name Super-LumiNova. This is a strontium aluminate-based non-toxic and non-radioactive material which has advantageously replaced radium-based luminescent paints. However, because the use of Super-LumiNova© material has become widespread in the watchmaking industry, the appearance of watches when they are viewed at night has become greatly standardised, making it difficult to distinguish between a given manufacturer's watch and a competitor's watch. All watch manufacturers strive to give their products a strong visual identity that sets them apart from competitors' watches.
Further, in wristwatches equipped with a light source, activation of the light source is usually achieved by means of a push-button located at a given place on the periphery of the watch case and which is therefore difficult to find when the user is fumbling in the dark.